The computational and energy cost of simulation and storage for climate science: lessons from CMIP6

The Coupled Model Intercomparison Project (CMIP) is one of the biggest international efforts aimed at better understanding the past, present, and future of climate changes in a multi-model context. A total of 21 model intercomparison projects (MIPs) were endorsed in its sixth phase (CMIP6), which included 190 different experiments that were used to simulate 40 000 years and produced around 40 PB of data in total. This paper presents the main findings obtained from the CPMIP (the Computational Performance Model Intercomparison Project), a collection of a common set of metrics, specifically designed for assessing climate model performance. These metrics were exclusively collected from the production runs of experiments used in CMIP6 and primarily from institutions within the IS-ENES3 consortium. The document presents the full set of CPMIP metrics per institution and experiment, including a detailed analysis and discussion of each of the measurements. During the analysis, we found a positive correlation between the core hours needed, the complexity of the models, and the resolution used. Likewise, we show that between 5 %–15 % of the execution cost is spent in the coupling between independent components, and it only gets worse by increasing the number of resources. From the data, it is clear that queue times have a great impact on the actual speed achieved and have a huge variability across different institutions, ranging from none to up to 78 % execution overhead. Furthermore, our evaluation shows that the estimated carbon footprint of running such big simulations within the IS-ENES3 consortium is 1692 t of CO2 equivalent. As a result of the collection, we contribute to the creation of a comprehensive database for future community reference, establishing a benchmark for evaluation and facilitating the multi-model, multi-platform comparisons crucial for understanding climate modelling performance. Given the diverse range of applications, configurations, and hardware utilised, further work is required for the standardisation and formulation of general rules. The paper concludes with recommendations for future exercises aimed at addressing the encountered challenges which will facilitate more collections of a similar nature

Ocean Biogeochemistry in GFDL’s Earth System Model 4.1 and its Response to Increasing Atmospheric CO2

This contribution describes the ocean biogeochemical component of the Geophysical Fluid Dynamics Laboratory's Earth System Model 4.1 (GFDL‐ESM4.1), assesses GFDL‐ESM4.1's capacity to capture observed ocean biogeochemical patterns, and documents its response to increasing atmospheric CO2. Notable differences relative to the previous generation ofGFDL ESM's include enhanced resolution of plankton food web dynamics, refined particle remineralization, and a larger number of exchanges of nutrients across Earth system components. During model spin‐up, the carbon drift rapidly fell below the 10 Pg C per century equilibration criterion established by the Coupled Climate‐Carbon Cycle Model Intercomparison Project (C4MIP). Simulations robustly captured large‐scale observed nutrient distributions, plankton dynamics, and characteristics of the biological pump. The model overexpressed phosphate limitation and open ocean hypoxia in some areas but still yielded realistic surface and deep carbon system properties, including cumulative carbon uptake since preindustrial times and over the last decades that is consistent with observation‐based estimates. The model's response to the direct and radiative effects of a 200% atmospheric CO2 increase from preindustrial conditions (i.e., years 101–120 of a 1% CO2 yr−1 simulation) included (a) a weakened, shoaling organic carbon pump leading to a 38% reduction in the sinking flux at 2,000 m; (b) a two‐thirds reduction in the calcium carbonate pump that nonetheless generated only weak calcite compensation on century time‐scales; and, in contrast to previous GFDL ESMs, (c) a moderate reduction in global net primary production that was amplified at higher trophic levels. We conclude with a discussion of model limitations and priority developments

CPMIP: measurements of real computational performance of Earth system models in CMIP6

International audienceA climate model represents a multitude of processes on a variety of timescales and space scales: a canoni-cal example of multi-physics multi-scale modeling. The underlying climate system is physically characterized by sensitive dependence on initial conditions, and natural stochastic variability, so very long integrations are needed to extract signals of climate change. Algorithms generally possess weak scaling and can be I/O and/or memory-bound. Such weak-scaling, I/O, and memory-bound multi-physics codes present particular challenges to computational performance. Traditional metrics of computational efficiency such as performance counters and scaling curves do not tell us enough about real sustained performance from climate models on different machines. They also do not provide a satisfactory basis for comparative information across models. We introduce a set of metrics that can be used for the study of computational performance of climate (and Earth system) models. These measures do not require specialized software or specific hardware counters, and should be accessible to anyone. They are independent of platform and underlying parallel programming models. We show how these metrics can be used to measure actually attained performance of Earth system models on different machines, and identify the most fruitful areas of research and development for performance engineering. We present results for these measures for a diverse suite of models from several modeling centers, and propose to use these measures as a basis for a CPMIP, a computational performance model intercomparison project (MIP)

NOAA-GFDL/FMScoupler: 2023.03

<p>No code changes were made to the coupler this release cycle, just tagging current main to be used alongside the corresponding FMS release.</p&gt

NOAA-GFDL/FMS: 2023.03

<h2>[2023.03] - 2023-10-27</h2> <h3>Known Issues</h3> <ul> <li>GCC 9 and below as well as GCC 11.1.0 are unsupported due to compilation issues. See prior releases for more details.</li> <li><code>NO_QUAD_PRECISION</code> macro is no longer set by FMS, the <code>ENABLE_QUAD_PRECISION</code> macro has replaced prior usage of <code>NO_QUAD_PRECISION</code>. <code>-DENABLE_QUAD_PRECISION</code> should be set if quad precision is to be used, otherwise FMS will not use quad precision reals where applicable.</li> </ul> <h3>Added</h3> <ul> <li>UNIT_TESTS: New unit tests have been created or and existing ones expanded on for any modules utilizing mixed precision support.</li> </ul> <h3>Changed</h3> <ul> <li>MIXED PRECISION: Most subroutines and functions in FMS have been updated to simultaneously accept both 4 byte and 8 byte reals as arguments. This deprecates the <code>--enable-mixed-mode</code> option, which enabled similar functionality but was limited to certain directories and was not enabled by default. To facilitate easier testing of these code changes, the CMake precision options for default real size were left in (along with an equivalent <code>--disable-r8-default</code> flag for autotools). The resulting libraries will support mixed-precision real kinds regardless of default real size. It should also be noted that many routines that accept real arguments have been moved to include files along with headers in order to be compiled with both kinds. Most module level variables were explicitly declared as r8_kind for these updates.</li> <li>Some type/module changes were made to facilitate mixed precision support. They are <strong>intended</strong> to have minimal impact to other codebases:<ul> <li>COUPLER_TYPES: In coupler_types.F90, <code>coupler_nd_field_type</code> and <code>coupler_nd_values_type</code> have been renamed to indicate real kind value: <code>coupler_nd_real4/8_field_type</code> and <code>coupler_nd_real4/8_values_type</code>. The <code>bc</code> field within <code>coupler_nd_bc_type</code> was modified to use r8_kind within the value and field types, and an additional field added <code>bc_r4</code> to use r4_kind values.</li> <li>TRIDIAGONAL: Module state between r4 and r8 calls are distinct (ie. subsequent calls will only be affected by calls of the same precision). This behaviour can be changed via the <code>save_both_kinds</code> optional argument to <code>tri_invert</code>.</li> </ul> </li> <li>CODE_STYLE: has been updated to reflect the formatting used for the mixed precision support updates.</li> </ul> <h3>Fixed</h3> <ul> <li>DIAG_MANAGER: Tile number (ie. tileX) will now be added to filenames for sub-regional diagnostics.</li> <li>MPP: Bug affecting non-intel compilers coming from uninitialized pointer in the <code>nest_domain_type</code></li> <li>MPP: Bug fix for unallocated field causing seg faults in <code>mpp_check_field</code></li> <li>FMS2_IO: Fixed segfault occuring from use of cray pointer remapping along with mpp_scatter/gather</li> <li>TEST_FMS: Added various fixes for different compilers within test programs for fms2_io, mpp, diag_manager, parser, and sat_vapor_pres.</li> <li>INTERPOLATOR: Deallocates fields in the type that were previously left out in <code>interpolator_end</code></li> </ul> <h3>Removed</h3> <ul> <li>CPP MACROS:<ul> <li><code>no_4byte_reals</code> was removed and will not set any additional macros if used. <code>no_8byte_integers</code> is still functional.</li> <li><code>NO_QUAD_PRECISION</code> was removed. It was conditionally set if ENABLE_QUAD_PRECISION was undefined. ENABLE_QUAD_PRECISION should be used in model components instead (logic is flipped)</li> <li><code>use_netCDF</code> was set by autotools previously but wasn't consistently used in the code. FMS should always be compiled with netcdf installed so this was removed with the exception of its use in deprecated IO modules.</li> </ul> </li> <li>DRIFTERS: The drifters subdirectory has been deprecated. It will only be compiled if using the <code>-Duse_drifters</code> CPP flag.</li> </ul> <h3>Tag Commit Hashes</h3> <ul> <li>2023.03-beta1 06b94a7f574e7794684b8584391744ded68e2989</li> <li>2023.03-alpha3 b25a7c52a27dfd52edc10bc0ebe12776af0f03df</li> <li>2023.03-alpha2 9983ce308e62e9f7215b04c227cebd30fd75e784</li> <li>2023.03-alpha1 a46bd94fd8dd1f6f021501e29179003ff28180ec</li> </ul&gt

Dietary n-6- or n-3-rich vegetable fats and antioxidants: effects on fatty acid composition and stability of rabbit plasma, liver and meat

We supplemented diets with a-tocopheryl acetate (100 mg/kg) and replaced beef tallow (BT) in feeds with increasing doses of n-6- or n-3-rich vegetable fat sources (linseed and sunflower oil), and studied the effects on the fatty acid (FA) composition, the a-tocopherol (aT) content and the oxidative stability of rabbit plasma and liver. These effects were compared with those observed in a previous study in rabbit meat. As in meat, the content of saturated, monounsaturated and trans FA in plasma and liver mainly reflected feed FA profile, except stearic acid in liver, which increased as feeds contained higher doses of vegetable fat, which could be related to an inhibition of the activity of the stearoyl-CoA-desaturase. As linseed oil increased in feeds, the n-6/n-3 FA ratio was decreased in plasma and liver as a result of the incorporation of FA from diets and also, due to the different performance and selectivity of desaturase enzymes. However, an increase in the dose of vegetable fat in feeds led to a significant reduction in the aT content of plasma and liver, which was greater when the fat source was linseed oil. Increasing the dose of vegetable fat in feeds also led to an increase in the susceptibility to oxidation (lipid hydroperoxide (LHP) value) of rabbit plasma, liver and meat and on the thiobarbituric acid (TBA) values of meat. Although the dietary supplementation with a-tocopheryl acetate increased the aT content in plasma and liver, it did not modify significantly their TBA or LHP values. In meat however, both TBA and LHP values were reduced by the dietary supplementation with a-tocopheryl acetate. The plasma aT content reflected the aT content in tissues, and correlated negatively with tissue oxidability. From the studied diets, those containing 1.5% linseed oil plus 1.5% BT and 100 mg of a-tocopheryl acetate/kg most improved the FA composition and the oxidative stability of rabbit tissues